Whether you were there on Nov. 15, 2013, or simply heard about it on the news, you, like millions around the world, probably were moved by the adventures of Batkid in San Francisco.

Director Dana Nachman’s new documentary “Batkid Begins” tells the whole story, from cowl to cape. It begins with Miles Scott, a northern California kid who was diagnosed with leukemia when he was 18 months old.

Miles missed out on a normal childhood as he underwent a series of brutal treatments. During the time, he discovered Batman, via TV reruns of the 1960s series, and became a fan.

When the Make-A-Wish Foundation determined that Miles qualified for a wish, he decided to be Batman. Patricia Wilson, executive director of the San Francisco chapter of Make-A-Wish, went into action, planning a day for the 5-year-old filled with rescues, chases and collars.

It grew more and more complex.

She hired acrobat-programmer Eric “E.J.” Johnston to play Batman, and he in turn recruited his wife Sue Graham Johnston to play a damsel in distress and his friend Mike Jutan, a computer engineer for ILM, to play the Penguin. Actor Philip Watt portrayed the Riddler, and Giants mascot Lou Seal volunteered to be kidnapped.

The big story was how a request for a couple of hundred sideline spectators turned into a flash mob of thousands.

Many fascinating smaller stories materialize. Nachman shows how E.J. builds a wrist projector to receive “reports” from San Francisco Police Chief Greg Suhr, and reveals the source of the Batkid suit.

Still, what makes “Batkid Begins” such a profoundly moving experience is the unbelievable human connection and camaraderie that sprung up on that day in November.

It’s a rare documentary that showcases the absolute best of humanity. Batkid participants, both marginal and essential, emphasize the day’s kindness, caring and cooperation, despite massive crowds.

Witnessing the interviewees repeatedly talk about being moved to happy tears, it’s easy to get choked up watching “Batkid Begins.” Surprisingly, the movie isn’t shameless and goopy. Nachman miraculously keeps it on track. Like its subject, it’s difficult to let negativity ruin it.

When you leave the theater, you even may feel like being a little extra nice to others. Now that’s a real superpower.